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Microbiology - Gram Positive > Clostridium > Flashcards

Clostridium Flashcards

1
Q

What are the spore forming bacteria?

A

Clostridium spp.
Clostridioides spp.
Bacillus spp.

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2
Q

How to classify?

A

Spore forming gram positive rods

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3
Q

What does it produce?

A

Exotoxins

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4
Q

What are the sources?

A

Environmental (soil), faeces of man and animals (esp. herbivores)

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5
Q

Name the 4 Clostridium species

A

C. perfringens, C.tetani, C.botulinum, Clostridioides difficile

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6
Q

What diseases does C.perfringens cause?

A

SSTI (Clostridial cellulitis, gas gangrene)
Food poisoning

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7
Q

What does gas gangrene of C.perfringens cause?

A

Muscle necrosis - myonecrosis
Severe pain
Loss of function
Gas in tissues (crepitation)
Fever
Shock
Multi Organ failure
Death

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8
Q

How to treat C.perfringens gas gangrene?

A
  1. Remove all dead and damaged tissue
  2. Penicillin G
  3. Clindamycin to reduce toxin production

Empirically add wider cover as don’t know what else is there

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9
Q

How to prevent C.perfringens gas gangrene?

A

Prophylactic antibiotics (for amputations or major trauma from environmental sources, devitalised tissue especially at risk)

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10
Q

How does C.perfringens cause food poisoning?

A

Meat stews etc./Raw meat contaminated with fecal flora
Spores survive inadequate cooking: germinate in gut and organism releases toxins

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11
Q

What toxin does C.perfringens make? Which toxin causes clostridial necrotising enteritis?

A

Many toxins but strains with beta toxin causes necrotising enteritis

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12
Q

Where does C.perfringens outbreaks occur?

A

Poor countries
- Chronic malnourished (episodic meat feasting, poor food hygiene)
- Staple diets containing trypsin inhibitors (ascaris which secretes trypsin inhibitors more common)

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13
Q

How is C.tetani transmitted?

A

Spores in soil get into wound and contaminate wound infection

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14
Q

What is the toxin for C.tetani?

A

Tetanospasmin toxin

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15
Q

What diseases does C.tetani cause?

A
  1. Risus sardonicus - jaw stiffness
  2. Tetanic spasms
  3. Spastic paralysis
  4. Opisthotonus - exaggerated arching of back
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16
Q

How to treat C.tetani spasms?

A

Human tetanus immunoglobulin (HTIG) to mop up toxin
Antibiotic
Immunise after recovery
Intensive support therapy
Severe cases: paralyse to relax muscles and ventilate

17
Q

Mechanism of action of C.tetani toxin

A

Tetanospasmin bocks release of inhibitory neurotransmitters (GABA, glycine) at lower motor neuron by cleaving SNARE proteins required for docking of vesicles -> Lower motor neurons receives only excitatory messages and fires continuously -> spastic paralysis

18
Q

How to prevent tetanus?

A
  1. Toxoid vaccine
  2. Assess wounds (Clean vs tetanus-prone)
    -> wound cleaning/debridement, vaccine booster/full course
  3. Injection of human tetanus immunoglobulin
  4. Antibiotics (metronidazole/penicillin)
19
Q

How does C.tetani look like under the microscope?

20
Q

What is the name of the disease that C.botulinum cause?

21
Q

How is C.botulism acquired?

A

Food borne

22
Q

Describe C.botulinum toxin

A

Usually pre-formed toxin in food with rapid onset
Less commonly toxin formed in wound or gut infection

23
Q

What does C.botulinum cause?

A

Flaccid paralysis
Infants - floppy baby syndrome
IV drug users - wound botulism

  • Early signs: diplopia, dysphagia, ptosis, nausea, vomiting, usually no fever
  • Severe conditions: paralysis of respiratory muscles (death!!)
24
Q

How to treat C.botulinum?

A

Antiserum to mop up toxin and ventilate

25
Q

Mechanism of action of C.botulinum toxin

A

Blocks release of acetylcholine at neuromuscular junction from lower motor neuron to muscle

26
Q

What diseases does C.diff cause?

A
  1. C.diff associated diarrhoea
  2. Pseudomembranous colitis
  3. May progress to toxic megacolon
27
Q

How is C.diff acquired?

A

Precipitated by an antibiotic which disturbs balance of normal flora -> overgrowth of anaerobic bacteria -> commensal becomes a pathogen

28
Q

How to diagnose C.diff?

A

Faeces sample:
-Enzyme immunoassay/culture to detect GDH antigen/organism
-Enzyme/cytotoxicity assay/PCR to detect toxin

29
Q

How to treat C.diff?

A
  1. Stop antibiotics if possible
  2. Oral vancomycin/Metronidazole
  3. Oral fidaxomicin
  4. IV Bezlotouxmab
  5. Faecal Microbial Transplant (if multiple relapses, very effective)
  6. Colectomy (RARELY)
30
Q

Infection control for C.diff

A
  1. Avoid antibiotics
  2. Isolate patient
  3. Enhanced cleaning, laundry, hand hygiene
  4. Use water and soap (NOT ALCOHOLIC HANDRUBS AS SPORES NOT DESTROYED)

Microbiology - Gram Positive (9 decks)

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